1. Field of the Invention
The invention relates to a respiratory half-mask comprising a mask body fitted with front or side filters, a head strap support with two side straps emanating from said support, which can be connected at the free ends, and a strap guide part fastened on the mask body for sliding the mask body along the side straps from a usage position covering mouth and nose into a position which exposes the face.
Respiratory half-masks are used for covering the mouth and nose of the user with a mask body which is configured with side filters or a front filter to protect the mask wearer from contaminants present in the air, and has at least one exhalation valve. The half-mask is usually held on the head of the user with the aid of a strap connected to the mask, consisting of side straps connected to a head support. The strap and its connection to the mask body should be designed such that the respiratory half-mask can be donned and doffed or adjusted simply and rapidly and can furthermore be held on the face of the mask wearer in a reliable sealing manner and with high wearing comfort, and specifically from the point of view of the heavy filter elements and a high physical stressing of the user. An important requirement with regard to the usage comfort of the respiratory half-mask consists in being able to remove the half-mask only temporarily from the mouth and nose, for example, in order to be able to reach the mouth only temporarily or because the surroundings are free from contaminants. Donning or doffing the half-mask is particularly complex if the strap is connected to a head support supported on the head of the user which is worn under a helmet which must be taken off and put on again every time the respiratory half-mask is donned or doffed.
2. Description of the Related Art
Known from EP 1 019 151 B1 is a respiratory half-mask with a strap guide part attached to the mask body in which the two side straps fastened to a head support are each guided in an upper guide and in a lower guide and are guided from the upper guide to the obliquely opposite lower guide so that they cross over each other. The four guides form an advantageous four-point holding of the mask body on the face of the user. The mask body can be moved along the side straps guided in the upper and lower guides from a position covering the mouth and nose of the user into a position located below the face or in the opposite direction. That is, the mask can be donned or doffed relatively rapidly and simply without needing to remove a protective helmet worn over the head support. However, the secure fit of the mask body and the reliable sealing on the face are limited insofar as the mask body can slip on the face as a result of the weight caused by the filters and under high physical stressing of the user, in particular in connection with moisture forming between the mask body and the face, and consequently a reliable seal is not ensured. For bracing the mask body on the face of the user, the side straps attached adjustably to the head support must be tensioned. The loose ends of the side straps hanging down from the head support, which are provided for firmly tightening the respiratory half-mask on the face of the user are perceived as interfering by the user.
A respiratory half-mask described in EP 0 808 641 B1 has a strap guide element on both outer sides for respectively one side strap connected to a head support, the free ends of which have a closure element to allow the two ends to be connected to one another behind the head. The two strap guide elements have an elongated curved slot in which the relevant side strap can run slidingly and in which it acquires the curved structure of the slot in order to enter into frictional engagement with the strap guide element but in which it can still move in a sliding manner. In this way, the half-mask can be adjusted by overcoming the frictional forces from a position abutting against the face into a position below the face which exposes the nose and mouth. The frictional forces are intended to prevent self-slippage of the half-mask from the face. Apart from the fact that only an unstable two-point holding of the half-mask on the face is ensured with the two strap guide elements, with the aid of the frictional forces on the side straps produced in the curved slot it is not possible to fix the mask body securely on the side straps, and therefore on the face, and in particular specifically not under physical stressing and corresponding vibrations. A significant increase in the frictional forces on the side straps guided in lateral strap guides, which has already been proposed, conflicts with the requirement for a simple and rapid adjustment of the half-mask in the respective position and high wear or damage to the side straps.
Known from WO 03/033077 A1 is a respiratory half-mask which likewise allows a rapid adjustment from a position sealingly covering the mouth and nose into a hanging-down position exposing the face. Detachably attached to the mask body is a strap guide element to which respectively one adjustable-length neck strap is fastened at two lower connecting points, the free ends whereof being connectable to one another behind the neck of the user. Two side straps connected to a head support and running in lateral guides are fastened at the lower edge of a locking flap which is connected pivotally to the strap guide element on the opposite edge. In the downward-pivoted locked position on the mask body, the mask body abuts against the face of the user. However, the side straps can also be re-tensioned on the head support. The two neck straps are connected to one another behind the neck and can also be re-tensioned. By pivoting the locking flap upwards, the length of the side straps is extended so that the respiratory half-mask can be removed from the face or, when the neck straps are released, held hanging on the head support below the face. This respiratory half-mask is disadvantageous insofar as neck straps must be provided along with the side straps and these must be braced in each case when donning the mask. In addition, the locking flap can easily work loose so that respiratory protection is not reliably ensured.